Lumen Mailable多个视图（如何？）

I have the a controller that calls a Mail class that fetches a view to be sent to an email. I was able to successfully retrieve a single view. But how do I concat multiple views together?

My controller:

namespace App\Http\Controllers; 

class TestController extends Controller
{
    public function sendMail(){
        $notification = new NotificationService();
        $notification->sendMail();
   }
}

Service:

namespace App\Services;


use App\Mail\Test;
use Illuminate\Support\Facades\Mail;


 class NotificationService
 {

      public function sendMail(){
         Mail::to(['test@email.com'])->send(new Test);
     }
}

Mail:

namespace App\Mail;

use Illuminate\Mail\Mailable;


class Test extends Mailable
{

   public function build()
   {
      $view = $this->getTestView(); 
      return  $view; 
    }

    private function getTestView(){
       return $this->view(['TestEmail']);
    }   

  }

I need to be able to put together multiple views in the Mail Test Class:

EG:

namespace App\Mail;

use Illuminate\Mail\Mailable;


class Test extends Mailable
{

   public function build()
   {
      $view  = $this->getTestView(); 
      $view2 = $this->getTestView2()
      return  $view . $view2; 
    }

    private function getTestView(){
       return $this->view(['TestEmail']);
    }  

    // HOW DO I CALL THIS IN THE build()? 
    private function getTestView2(){
       return $this->view(['TestEmail2']);
    } 

  }

Just make a new view that includes both

FullEmail.blade.php

@include('TestEmail')
@include('TestEmail2')